The data on recovery of infectious virus must be interpreted in relation to the amount of antibody in the test material. Table 4 shows results of HI tests on the serums and tissue extracts from experiment 1, and table 2, column 4, shows HI tests on serums from experiment 2. To evaluate the content of nonspecific inhibitors as well as of antibody, the tests on tissue extracts were made on the untreated material and on the same suspension after treatment with RDE; the inhibition of HA by the untreated suspension represents the effect of both inhibitor and antibody, while inhibition by the RDE-treated material represents antibody alone. During the peak phase of virus growth, HI tests were often not possible because of hemagglutinin in the tissue suspensions,fpar-ticularly those treated with RDE. Antibody appeared in serum, at the level of testing, on the 10th day of infection, and rose progressively through the 20th to 30th day, generally reaching titers of 1:1600 to 1:6400. Antibody in tissues was readily demonstrable after the 14th day, with titers in general agreement with that expected by their content of blood.

Table 4. Ha Inhibitors In Tissue Suspensions Obtained At Intervals After Inoculation Of Newborns: Experiment 1

HI titers*

Blood clot

Pooled viscera Salivaryglands

Kidneys

Thymus

Lungs Liver

Spleen

Brain

Days of

Un-

RDE-

Un-

RDE-

Un-

RDE-

Un-

RDE-

Un-

RDE-

TJn-

RDE- TJn-

RDE-

Un-

RDE-

Un-

RDE-

harvest

Group

Serum

treated

treated

treated treated treated treated treated treated treated treated treated treated treated treated treated treated treated treated

2

1

<100 (pool)

160

<20

4

2

<100 (pool)

20

20

7

3

<100 (pool)

NT†

NT

7

4

<100 (pool)

<20

(20)

>320

NT

NT

NT

NT

NT

<10

<20 <10

NT

<10

NT

<10

<10

7

5

<100 (pool)

<20

<20

NT

NT

NT

NT

NT

NT

20

NT <10

NT

<10

NT

(10)

(10)

10

6

60; 200; 200; 400

<80

<20

10

7

200; 200; 400; 3200

40

40

>1280

<20

NT

NT

<10

<10

<10

NT <20

<20

<10

<20

40

<10

14

8

200; 200; 1600

320

320

20

9

3200 (pool)

160

160

20

10

800; 1600; 1600; 3200

>1280

1280

>1280

40

160

80

<20

<20

320

320 80

80

<20

<20

40

40

30

U

6400 (pool)

640

320

30

12

3200; 3200; 6400; 6400

>1280

>1280

>1280

>1280

640

640

320

<40

640

640 >1280

>1280

160

320

80

80

60

13

6400; 6400; 6400; 12,800

>1280

>1280

90

14

3200; 6400; 6400; 6400

1280

1280

90

16

3200; 6400; 6400; 25,600

6120

2660

6120

1280

120

16

640

640

2560

1280

120

17

320

160

640

320

120

18

3200; 6400; 12,800; 12,800

640

1280

1280

2660

640

2660

2660

> 1,240 1280

2660

320

640

160

640

133

19

26,600

144

20

61,200

800

144

21

26,600

1600

*HI titer of serum expressed per 0.2 ml. of serum; titers of all other tissues expressed per 0.2 ml. of 10 percent suspension. †NT - No test because of HA by the tissue suspension.

Table 5. Representative Titrations Of Parotid Tumor Suspensions By Map And Tissue-Culture Tests

HI antibody titers*

Result of assay of serial dilutions of tumor extract by MAP or tissue-culture tests †

Parotid tumor

Serum

Tumor extract

Test

10^0

10^-1

10^-2

10^-3

10^-4

10^-5

10^-6

Expt. 1, group 15

3200-25,600

1280

MAP

1/2‡

0/3

2/3

3/3

3/3

1/3

Expt. 1, group 15

MAP

2/2

2/3

3/3

1/3

2/3

1/3

0/3

Expt. 1, group 18

3200-12,800

1280

MAP

0/3

2/3

3/3

2/3

Expt. 1, group 18

MAP

3/3

2/2

2/2

2/3

0/3

0/3

Expt. 1, group 20

51,200

800

MAP

2/3

2/3

1/3

1/3

0/3

Expt. 1, group 20

ME TC

0/3 §

2/3

1/3

1/2

0/2

0/3

Expt. 1, group 21

25,600

1600

MAP

0/3

1/3

1/2

1/3

0/3

1/3

Expt. 1, group 21

ME TC

0/2

1/3

2/3

1/3

0/2

0/3

*Titers expressed per 0.2 ml. of serum and per 0.2 ml. of RDE-treated 10 percent tumor suspension.

† Results of 35-day MAP tests and mouse embryo tissue cultures observed for 30 days.

‡ Numerator = number of mice developing HI antibody. Denominator = number of mice inoculated.

§ Numerator = number of tissue-culture tubes demonstrating cytopathlc effects and/or hemagglutinin. Denominator = number of tubes observed.

Nonspecific inhibitor was found in salivary glands in high titer, which was anticipated from the mucoprotein nature of the erythrocyte receptors necessary for polyoma HA (6).

Detection and quantitation of virus in tissues taken late in infection were hampered by the high level of antibody in the tissue suspension. Whereas titrations of tissue extracts taken early in infection gave sharp titration endpoints in the MAP test, the late suspensions gave irregular antibody response over a wide dilution range. Occasionally parotid tumor suspensions gave prozones in MAP or tissue-culture titrations, presumably due to reactivation by dilution. Table 5 shows results of representative titrations of parotid tumor suspensions illustrating these points.

It should be noted that in other experiments we have twice encountered parotid tumor suspensions which gave no evidence of infectivity when titered in MAP and mouse embryo tissue-culture tests, but which yielded specific hemagglutinin and virus when the tumor tissue was grown in explant type culture in roller tubes.